It is known to transmit messages using a telex. In telex communication, coded digits are transmitted from one terminal to another, which is dialled up using a number found from a publicly available directory. The receiving terminals signals back to indicate that contact has been made, and acknowledge receipt of a message. The message is printed at the receiving terminal.
It is also known to communicate messages by facsimile. In facsimile transmission, a document is scanned and encoded using image compression coding. The encoded image (not the text it represents) is transmitted to a facsimile receiver, where it is printed out.
Text may also be transmitted using electronic mail systems, in which a transmitting terminal dials up a central message storage computer and transmits a message to be stored under a designated mailbox therein. The intended recipient of the message will then later dial the central computer and read his message. Similar text communication systems include bulletin board systems, in which messages are stored in a bulletin board computer and subsequently read by the intended recipient.
The above systems may thus be divided into point to point systems (telex and facsimile) in which messages are transmitted direct to the recipient, and stored and collect systems (electronic mail) in which a message is deposited in a mailbox and then subsequently read.